Date:	Thu, 18 Aug 2016 11:01:11 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	David Rientjes <rientjes@...gle.com>,
	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 03/11] mm, compaction: rename COMPACT_PARTIAL to
 COMPACT_SUCCESS

On Wed 10-08-16 11:12:18, Vlastimil Babka wrote:
> COMPACT_PARTIAL has historically meant that compaction returned after doing
> some work without fully compacting a zone. It however didn't distinguish if
> compaction terminated because it succeeded in creating the requested high-order
> page. This has changed recently and now we only return COMPACT_PARTIAL when
> compaction thinks it succeeded, or the high-order watermark check in
> compaction_suitable() passes and no compaction needs to be done.
> 
> So at this point we can make the return value clearer by renaming it to
> COMPACT_SUCCESS. The next patch will remove some redundant tests for success
> where compaction just returned COMPACT_SUCCESS.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  include/linux/compaction.h        |  8 ++++----
>  include/trace/events/compaction.h |  2 +-
>  mm/compaction.c                   | 12 ++++++------
>  mm/vmscan.c                       |  2 +-
>  4 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
> index 1bb58581301c..e88c037afe47 100644
> --- a/include/linux/compaction.h
> +++ b/include/linux/compaction.h
> @@ -49,10 +49,10 @@ enum compact_result {
>  	COMPACT_CONTENDED,
>  
>  	/*
> -	 * direct compaction partially compacted a zone and there might be
> -	 * suitable pages
> +	 * direct compaction terminated after concluding that the allocation
> +	 * should now succeed
>  	 */
> -	COMPACT_PARTIAL,
> +	COMPACT_SUCCESS,
>  };
>  
>  struct alloc_context; /* in mm/internal.h */
> @@ -88,7 +88,7 @@ static inline bool compaction_made_progress(enum compact_result result)
>  	 * that the compaction successfully isolated and migrated some
>  	 * pageblocks.
>  	 */
> -	if (result == COMPACT_PARTIAL)
> +	if (result == COMPACT_SUCCESS)
>  		return true;
>  
>  	return false;
> diff --git a/include/trace/events/compaction.h b/include/trace/events/compaction.h
> index c2ba402ab256..cbdb90b6b308 100644
> --- a/include/trace/events/compaction.h
> +++ b/include/trace/events/compaction.h
> @@ -13,7 +13,7 @@
>  	EM( COMPACT_SKIPPED,		"skipped")		\
>  	EM( COMPACT_DEFERRED,		"deferred")		\
>  	EM( COMPACT_CONTINUE,		"continue")		\
> -	EM( COMPACT_PARTIAL,		"partial")		\
> +	EM( COMPACT_SUCCESS,		"success")		\
>  	EM( COMPACT_PARTIAL_SKIPPED,	"partial_skipped")	\
>  	EM( COMPACT_COMPLETE,		"complete")		\
>  	EM( COMPACT_NO_SUITABLE_PAGE,	"no_suitable_page")	\
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 328bdfeece2d..c355bf0d8599 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1329,13 +1329,13 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
>  
>  		/* Job done if page is free of the right migratetype */
>  		if (!list_empty(&area->free_list[migratetype]))
> -			return COMPACT_PARTIAL;
> +			return COMPACT_SUCCESS;
>  
>  #ifdef CONFIG_CMA
>  		/* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */
>  		if (migratetype == MIGRATE_MOVABLE &&
>  			!list_empty(&area->free_list[MIGRATE_CMA]))
> -			return COMPACT_PARTIAL;
> +			return COMPACT_SUCCESS;
>  #endif
>  		/*
>  		 * Job done if allocation would steal freepages from
> @@ -1343,7 +1343,7 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
>  		 */
>  		if (find_suitable_fallback(area, order, migratetype,
>  						true, &can_steal) != -1)
> -			return COMPACT_PARTIAL;
> +			return COMPACT_SUCCESS;
>  	}
>  
>  	return COMPACT_NO_SUITABLE_PAGE;
> @@ -1367,7 +1367,7 @@ static enum compact_result compact_finished(struct zone *zone,
>   * compaction_suitable: Is this suitable to run compaction on this zone now?
>   * Returns
>   *   COMPACT_SKIPPED  - If there are too few free pages for compaction
> - *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
> + *   COMPACT_SUCCESS  - If the allocation would succeed without compaction
>   *   COMPACT_CONTINUE - If compaction should run now
>   */
>  static enum compact_result __compaction_suitable(struct zone *zone, int order,
> @@ -1388,7 +1388,7 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
>  	 */
>  	if (zone_watermark_ok(zone, order, watermark, classzone_idx,
>  								alloc_flags))
> -		return COMPACT_PARTIAL;
> +		return COMPACT_SUCCESS;
>  
>  	/*
>  	 * Watermarks for order-0 must be met for compaction. Note the 2UL.
> @@ -1477,7 +1477,7 @@ static enum compact_result compact_zone(struct zone *zone, struct compact_contro
>  	ret = compaction_suitable(zone, cc->order, cc->alloc_flags,
>  							cc->classzone_idx);
>  	/* Compaction is likely to fail */
> -	if (ret == COMPACT_PARTIAL || ret == COMPACT_SKIPPED)
> +	if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
>  		return ret;
>  
>  	/* huh, compaction_suitable is returning something unexpected */
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 374d95d04178..c84784765d3a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2514,7 +2514,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
>  			continue;
>  
>  		switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
> -		case COMPACT_PARTIAL:
> +		case COMPACT_SUCCESS:
>  		case COMPACT_CONTINUE:
>  			return false;
>  		default:
> -- 
> 2.9.2
> 
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-- 
Michal Hocko
SUSE Labs

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